I'm not sure that generalization holds true. A lot of people play multiple persistent games, while not all of them feature large installs (Warframe is ~38 GB and POE is ~31 GB)), some are fairly heft (Destiny 2 is ~87 GB and GTA 5 is over 90 GB), and some are pretty massive (the aforementioned COD at 175 GB and RDR 2 is over 150 GB).
This doesn't even include racing games (Forza Horizon 4 without DLC is already 63 GB) or sports games (Fifa 20 is almost 50 GB without DLC) which I don't play.
This also doesn't include PC mods for games that can greatly inflate install size.
While a lot of people certainly uninstall games fairly rapidly, there are also a lot of people that keep multiple games installed because they play them either frequently or occasionally.
While I can certainly afford to have a 2TB drive in my machine for persistent games, not everyone is willing to spend that much just for games. And even here I often have to uninstall games before I have a chance to finish them (Metro: Exodus and Gears 5 [w/HD texture pack] for example) because I run out of space for new games I'd like to try out.
It can be a bit frustrating. Heck, one of the reasons I had to stop playing FFXIV and GW2 is that I had to choose games to stop playing to free up space on a 2 TB SSD or buy another SSD for games.
Regards,
SB